The present invention relates to a thrust reverser for a turbofan-type turbojet engine in which pivotable thrust reverser doors direct the flow of air through a cascade structure to provide thrust reversing forces.
Turbofan-type turbojet engines are well known in the art and, typically, comprise an annular housing concentrically arranged around the tubojet engine housing to define an annular cold-flow air duct extending along the longitudinal axis of the engine. A fan, driven by the turbojet engine, is usually located in the upstream portion of the cold-flow air duct to force air through the duct and augment the thrust of the tubojet engine.
In such turbofan-type turbojet engines having a relatively high bypass ratio, a thrust reversing device may by associated with the annular housing to redirect the air passing through the cold-flow air duct to provide a thrust reversing force. It is known to provide one or more pivotable thrust reversing doors in the annular housing to redirect the cold-flow air through one or more lateral openings in the housing.
A cross-sectional view of a typical prior art installation is illustrated in FIG. 1. The structure comprises an upstream annular housing portion 1, a thrust reverser 2 and a downstream annular housing portion 3. The upstream housing portion 1 comprises an outer surface panel 4 and an inner surface panel 5 interconnected by a frame structure 6. Similarly, downstream housing portion 3 has an inner surface panel 3a and an outer surface panel 3b.
The thrust reverser 2 comprises a pivotable door 7 and an actuator 7a extending between the door 7 and the frame structure 6. The actuator 7a, which may be a hydraulic cylinder, is attached to the frame structure 6 and has an extendible and retractable rod attached to pivoting door 7.
The door 7 extends between upstream housing portion 1 and downstream housing portion 3 so as to normally cover a generally laterally facing opening defined by the housing when the turbofan engine operates in the forward thrust mode. In this mode, as illustrated in FIG. 1, the outer door panel 9 is substantially flush with the outer surface panel 4 and the outer downstream surface panel 3b to provide a smooth air flow (indicated by arrow 10) over the exterior of the housing.
The piston rod of the actuating cylinder 7a is connected to the internal structure 12 of the thrust reverser door 7. Internal structure 12 interconnects the outer door panel 9 with the inner door panel 11, which panels are also connected at their upstream edges by baffle member 13.
In known fashion, extension of the piston rod of actuator 7a causes the door 7 to pivot with respect to the housing such that its upstream end portion swings outwardly while its downstream end portion swings inwardly to block off the air flow 15 flowing through the cold-flow air duct. The air is redirected by the door outwardly through the lateral opening in the annular housing to provide a thrust reversing force. When the door is in the open, thrust-reversing position, deflection edge 8, extending from the inner housing panel 5, minimizes the turbulence of the air passing outwardly through the opening. Baffle member 13 imparts a forward vector to the air passing through the lateral opening to increase the efficiency of the thrust reverser. In order to achieve the maximum efficiency, baffle member 13 must extend beyond the surface of the inner door panel 11.
When the door is in its closed position, as illustrated in FIG. 1, an internal cavity 16 is formed, bounded by the inner door panel 11, the extending portion of the baffle member 13, the deflection edge 8 and a theoretical air flow line 14 extending between the inner surface panel 5 and the inner surface 3a of the downstream housing portion 3. Line 14 represents the ideal theoretical air flow through the cold-flow air duct. The presence of cavity 16 causes disturbances in the air flow 15, thereby reducing the efficiency of the device in the forward thrust mode.
Typical examples of such known thrust reversing systems may be found in U.S. Pat. Nos. 4,410,152 and 4,485,970 as well as French Patent 2,559,838 and British Patent 1,181,746.
Various systems have been proposed to eliminate the presence of cavity 16, while still maintaining the efficiency of the baffle member 13. Such systems have included movable baffle members, as well as inner door panels which move relative the outer door panel as the door is moved between its opened and closed positions. While these systems have achieved a modicum of success, they inherently result in a thrust reversing door system of undesired complexity.
U.S. Pat. No. 3,605,411 discloses a thrust reverser door having an inner panel and an outer panel wherein the inner panel is movable with respect to the outer panel. When the thrust reverser door is in its closed position, the inner panel generally follows the theoretical air-flow line between the upstream and downstream portions. When in its open position, the inner door panel pivots through a greater angle such that its upstream portion is closer to the outer panel when opened than when closed. French Patent 2,638,207 also describes a thrust reverser having a pivotable door wherein an external door panel and an internal door panel are connected to each other and are movable with respect to each other.
The aforementioned French Patent 2,559,838 describes a pivoting thrust reverser door having an upstream baffle to direct the flow of thrust reversing gases in a particular direction. While generally successful, this particular type of thrust reverser door has been unable to provide the directional control to the thrust reversing gases necessary in a turbofan-type turbojet engine mounted in the tail of an aircraft. When mounted in this position, it is imparative that the thrust reversing gases be controlled so as to not impinge upon the aircraft control surfaces.